InterviewSolution
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InterviewSolution
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A dc ammeter and a hot wire ammeter are connected to a circuit in series. When a direct current is passed through circuit, the dc ammeter shows 6 A. When ac current flows through circuit, the ac ammeter shows 8A. What will be reading of each ammeter if dc and ac current flow simulataneously through the circuit?A. dc=6 A, ac=10AB. dc=3 A, ac=5AC. dc=5 A, ac=8AD. dc=2 A, ac=3A |
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Answer» Correct Answer - A Resultant current is superposition of tow currents, i.e. I(instantaneous total current ) `=6+(I_0) sin omega t` dc ammeter will read average value `=bar(6+(I_0)sin omega t) = 6` `(: Bar((I_0) sin omega t =0))` ac ammeter will read `=sqrt((bar(6+(I_0)sin omega t^(2)))` `=sqrt(bar(36+12 I_(0) sin omega t +I_(0)^(2) sin ^(2)omega t))` (`because bar(I_(0)si omega t =0))` since `bar(sin^(2) ometa t)=1/2 and (I_(rms))=8=(I_0)/(sqrt(2) implies (I_0)= 8 sqrt(2)A` Therefore ac reading `=sqrt(36 + (I_(0)^(2))/(2)) = sqrt(36 + 64) = 10 A`. |
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